Many functions of modern devices in automotive, consumer and industrial applications such as converting electrical energy and driving an electric motor or an electric machine rely on semiconductor devices. It is often desirable that rectifying semiconductor devices such as diodes and IGBTs (Insulated Gate Bipolar Transistors) have a sufficiently high blocking capability. Accordingly, their rectifying pn-junction or pn-junctions are often desired to withstand sufficiently high reverse voltages. Unfavorable dimensioning may result in avalanche generation close to or at points where the rectifying pn-junctions reaches a surface of the semiconductor material. Accordingly, blocking capability may be reduced to values well below the value of the bulk breakthrough voltage of the semiconductor material.
To minimize reduction of blocking capability due to rectifying pn-junctions which approach a surface of the semiconductor device, planar edge-termination structures and/or vertical edge-termination structures may be used, typically in a peripheral area of the semiconductor device, to redistribute the electric field in the blocking mode.
Planar edge-termination structures such as field plates, guard-ring structures or channel stop regions may be arranged on a main horizontal surface of the semiconductor device. Often a combination of several edge-termination structures is used. To achieve high blocking capability and stability, a comparatively large peripheral area is typically required when planar edge-termination structures are used. Furthermore, the size of the peripheral area typically rises with rated blocking voltage. For example, for a rated blocking voltage of 600 V a field-plate with a horizontal extension of at least about 200 μm is typically used. For a rated blocking voltage of about 6.5 kV the horizontal extension of the field-plate is typically larger than about 2 mm. Accordingly, the ratio between the size of the active area for switching and/or controlling the load current and the size of the peripheral area typically decreases with increasing rated blocking voltage.
Different thereto, vertical edge-termination structures, also known as mesa edge-termination structures, typically require less space. However, forming these structures is often associated with increased processing requirements e.g. for grinding when combined with MOS-technology.